Technological Field
The present invention relates to controllers, calibration control programs, and calibration control methods, and more particularly, to a controller that controls an image forming device that performs calibration, a calibration control program to be executed by the controller, and a calibration control method to be implemented in a printing system that includes the image forming device and the controller.
Description of the Related Art
In a copying machine or multi-functional peripherals (MFP) having a color print function, or more particularly, in an image forming device such as a product printing (PP) machine, the colors in printed materials change over time. Therefore, calibration is performed to adjust printed image quality. This calibration is automatically performed after printing has been performed on a certain number of paper sheets, or is forcibly performed by an operator. In many cases, calibration is performed at least once a day, or is performed every morning when the machine is activated, for example.
The above calibration is known by various names, such as color output stabilization, tone correction, and density adjustment, and can be performed in various manners. Examples of calibration methods include: a method of adjusting image quality by applying toner onto a photosensitive member or a transfer belt, and measuring the density of the toner, without any printing performed on a paper sheet; and a method of adjusting image quality by printing a measurement page having a measurement pattern formed thereon, scanning and measuring the measurement page with a density meter and a scanner provided in the image forming device, and comparing a set output value with the measured actual output value. By the former method, image quality can be adjusted, without any printing performed on a paper sheet. Thus, paper sheets are not unnecessarily consumed. However, the image quality adjustment cannot reflect sheet types, fixing conditions, and the like. By the latter method, paper sheets are consumed, but image adjustment is performed on each completed printed material. Thus, image quality can be accurately adjusted.
There are different kinds of calibration: calibration designed mainly to adjust an output value to a value close to a design target by adjusting the voltage to be used for charging the development device in the image forming device or for transfer (this kind of calibration will be hereinafter referred to as engine calibration); and calibration designed mainly to adjust the design target to the customer's liking by increasing or decreasing the numerical value to be output as data (this kind of calibration will be hereinafter referred to as controller calibration).
As for a technology to control such calibration, JP 10-063047 A discloses a control device that controls an image forming unit having a calibration function for correcting image quality variation in output images, for example. The control device includes: a detecting unit that detects a state change that requires calibration; and an output unit that outputs calibration information for prompting calibration when the detecting unit detects the state change.
Also, JP 03814342 B1 discloses an image processing device connected to external devices via a network. The image processing device includes: a detecting unit that detects a change in the state of an image forming unit; an inquiring unit that sends an inquiry to an external device when a change in the state of the image forming unit is detected, the inquiry being as to whether calibration is to be performed, the external device having issued the instruction as to the image output job currently being executed; a noticing unit that issues a calibration notice to the external devices other than the external device that has issued the instruction as to the image output job currently being executed; an input unit to which an instruction from the external device that has received the inquiry is input; and a control unit that controls the calibration timing in accordance with the instruction.
As for a technology to save time and image formation materials, though not a technology related to calibration, JP 2014-059490 A discloses an image forming device that includes a temperature detecting unit that measures the temperature of an appropriate portion in the image forming device, and, from the measured temperature, generates information indicating the image formation environment of an engine unit that might affect the position of image formation performed by an image forming unit, for example. In a case where the temperature variation during the time from the execution of the latest correction till the present time is determined to be within a predetermined range with respect to each of the colors other than a reference color, the image forming device determines that positioning correction for the current printing is unnecessary.
In many high-performance image forming devices, one of controllers developed and manufactured by different manufacturers is selected as a controller that rasterizes each print job output from a client device. The selected controller has a unique measurement pattern for controller calibration, taking advantage of its own features. This measurement pattern differs from the measurement pattern for engine calibration (differs in the amount of density change in each patch, for example).
Therefore, a user needs to conduct both engine calibration and controller calibration, and measurement patterns suitable for the respective kinds of calibration need to be formed and measured. As a result, the user needs to take a lot of trouble, and a larger amount of paper is consumed in printing the measurement patterns. Particularly, in the case of a color image forming device, toners of the four colors C, M, Y, and K are required, and measurement patterns need to be formed for the respective colors in some cases. Therefore, a user needs to take greater trouble, and the consumption of paper in printing the measurement patterns becomes even larger.
Even if the techniques disclosed in JP 10-063047 A, JP 03814342 B 1, and JP 2014-059490 A are used to control calibration in solving the above problem, both engine calibration and controller calibration still need to be performed. Therefore, the above problem is not solved.